Other causes of dental erosion are: bulimia, gastric reflux, abnormal salivary flow, reduced salivary efficiency, unusual eating and drinking habits, vapors in a chemical factory, etc.⁹

Professional (competitive) swimmers frequently train for several hours at a time in pools, which may predispose them to increased acid erosion. Acid erosion of dental enamel—ie, “swimmer's erosion”—is a painful, costly, irreversible condition, which can be caused by inadequately maintained gas-chlorinated swimming pools. Exposure to chlorine from a typical swimming session is roughly equivalent to occupational chlorine exposures.¹⁰

If sodium hypochlorite is used as the source for chlorine, which has an alkaline pH, then there won’t be any potential to cause erosion in teeth.¹¹ However, it is now common for economic reason for swimming pools to be chlorinated with chlorine gas instead of hypochlorite, which leads to the formation of hydrochloric and hypochlorous acids after interacting with the pool water. This gives rise to an acidic environment, with pH ranging from 2.7 to 4.0.^12,13 Proper buffering is required to maintain the pH of pool water to be between 7.2 to 7.8.¹⁴ If a gas-chlorinated pool becomes inadequately buffered through the addition of inadequate quantities of soda ash, the pH may decrease rapidly—for example, in one observed instance, it decreased from a pH of 7.4 to approximately 4.0 overnight.¹² Also, consumption of hydrochloric acid tablets was found to be strongly associated with severe enamel erosion.¹⁵

Acid erosion among competitive swimmers was found in 39% of swim-team members who trained in a pool with a pH of 2.7, which is a hydrogen ion concentration 100,000 times higher than that recommended for swimming pools.10 Data from 30 individuals who met the case definition and 60 control swimmers matched for age, race, and sex showed that 13% of cases had clinically evident general enamel erosion, compared to none in the control group.¹⁶

In India, regulations are generally overlooked and not followed according to the strictest guidelines. Therefore, swimming pool hygiene and maintenance may be below standards. Again, day-to-day maintenance activities such as attention to the amount of chlorine, the type of chlorination, pH of pools, proper buffering systems, water sanitation, etc., require regular monitoring. The prevalence of dental problems in regular swimmers might be very high. To date, there is no data available on the effect of swimming pool water on the dental health of competitive swimmers in India. Therefore, the present study was designed to find the prevalence and association of dental erosion in competitive swimmers.

Material and Methods

Three examiners examined 100 individuals (75 males mean age 18.6 ± 6.3 years and 25 females mean age 15.3 ± 7.02 years) who met the case definition criteria and were matched for age and race. Examiners were trained in advance to assess clinical findings like dental erosions (DE) and rough surfaces (RS). The inter-examiner’s analysis (by Kappa statistics > 0.85) was done before starting the pilot study. The examiners were calibrated and inter-examiner reliability checked to standardize data collection and to minimize measurement variations. The swimmers were checked at the 25th Silver Jubilee State Level Swimming Competition, held at Thane Municipal Corporation’s (TMC) Swimming Pool, Thane (Mumbai), India.

Data was collected in the form of structured questionnaires and clinical examinations for presence/absence of dental erosion cavities and rough teeth surfaces. Apart from erosion lesions, rough surfaces included: chalky white rough areas, fractured crowns, attrition/attrition-like/abfraction defects, and gritty and grossly uneven surfaces. For the pain perception, a visual analog scale was used and the subjects were asked to mark on the line provided in the questionnaire. Among the congregation, the swimmers have competed at state, national, and local levels, and several were training for competitive swimming. The questionnaires consisting of objective criteria were circulated among swimmers and recollected. In this trial, the investigators considered the ethical, legal, and regulatory norms and standards for research involving human subjects in India. Written consent was not sought from each participant for use of survey data, but consent of respondents was assumed and reaffirmed for clinical examinations after they completed and returned the questionnaire.

Excluded from the study were irregular/casual swimmers; swimmers with a history of gastric reflux, hyperacidity, bulimia, or an occupation in a chemical factory; those with adverse/abrasive teeth-cleaning habits; and those with a diet including citrus fruits.

Statistical Analysis

Statistical analysis was performed with the SPSS statistical software (SPSS Modeler, IBM, https://www-01.ibm.com/software/analytics/spss/products/modeler). Frequency distribution analysis for dental erosion, pain, and rough surfaces was done in relation to the hours and years of swimming.

Results

A total of 135 competitive swimmers completed and returned the questionnaire form. Among them, 35 individuals were excluded for various reasons, such as: history of gastric reflux and citrus fruit consumption and related case definition criteria (20), failure to submit to the clinical examination (9); and incompletely filled out questionnaires (6).

Among the 100 swimmers, 90% had dental erosion (DE) (Figure 1) and 94% had rough surfaces (RS). The prevalence of erosion and rough surfaces was found to be more with increasing duration of swimming per day (Table 1). Those who were regularly swimming for < 2 hours showed 20% DE and 40% RS; those swimming for 2 to 4 hours showed 93.9% DE and 96.3% RS; and those who were swimming for > 4 hours showed 92.3% DE and 100% RS, respectively.

Similar findings related to the number of years of regular swimming and the prevalence of erosion and rough surfaces were noted (Table 2). Those who had been swimming for 0 to 3 years, 4 to 7 years, 8 to 11 years, 12 to 15 years, and more than 15 years showed (0% DE, 0% RS), (86.5% DE, 92.3% RS), (97.2% DE, 100% RS), (100% DE, 100% RS) and (100% DE, 100% RS), respectively.

History of pain was also strongly correlated with the presence of dental erosion and rough surfaces; 72.7% erosions were associated with swimmers having a history of no pain, but 93% to 96% of erosions were found in patients giving a history of mild to severe pain (Table 3).

More than 60% of the swimmers were aware that one or more of their fellow swimmers were suffering or had suffered from dental problems because of swimming; and 88% of the participants were found to be experiencing pain in their teeth to various degrees and severity in this study.

Various other clinical observations included: white brittle-like look of teeth crowns, “chalky” white teeth; yellow discoloration, increased transparency; erosion of enamel, gritty or rough teeth; sensitivity of teeth; painful teeth, including while chewing; sour taste in the mouth; attrition-like defects; and fracture of crowns (Figure 2) caused by injury from pool walls, commonly involving upper and lower anterior teeth.

Discussion

Tooth enamel does not decalcify in acidic solutions unless the pH is below 6.0. Even at a pH between 5 and 6, hours of cumulative exposure are required for clinically evident decalcification to occur.¹⁷ As professional/competitive swimmers train for hours and days together to improve their swimming skill, their cumulative exposures obviously cannot be discounted. Strenuous physical activity, stress, and dehydration associated with this sport may also precipitate enamel erosion. On the other hand, pool maintenance seems to be a perpetual problem. The data issued by the US Centers for Disease Control (CDC)¹⁸ showed very serious observations on US pools. The majority (54.1%) of inspections from pool inspectors’ data from 2002 found one or more violations, and 8.3% of inspections resulted in immediate closure of the pool pending corrections of serious violation items (eg, lack of disinfectant). Of total violations, water-chemistry violations comprised 38.7%, followed by filtration and recirculation system (38.6%), and policy and management (22.7%).

In 2008, similar findings were noted by the CDC.¹⁹ The number of code violations identified ranged from 0 to 28, and 61.1% inspections identified one or more violations. A total of 12.1% inspections identified serious violations that threatened the public’s health and resulted in immediate pool closure. Of 120,975 inspections, 10.7% identified disinfectant level violations; of 113,597 inspections, 8.9% identified pH-level violations. Other water-chemistry violations documented accounted for 12.5%. Circulation and filtration violations documented were 35.9%. There is no authoritative data on the state of regular pool maintenance in India.

The severity of erosion lesions has been graded by Eccles and Jenkins²⁰ as follows: 0, when there is no involvement; 1, when there is loss of labial, lingual, or occlusal surface enamel, resulting in a smooth glazed appearance but no dentinal involvement; 2, when there is involvement of the dentin over less than one-third of the tooth surface area; and 3, when there is involvement of the dentin over more than one-third of the tooth surface area. The study authors considered only presence or absence of erosion as the criteria for diagnosis and correlated it with the questionnaire as presence of pain and sensitivity.

The prevalence of dental problems noted was on the higher scale; in addition, 88% of the participants were found to be experiencing pain in their teeth to various degrees in severity. Probable causes of the high prevalence of dental erosion among swimmers likely include: poor knowledge of dental health among Indian societies; lack of awareness of preventive measures; uncontrolled maintenance of the pool water; lack of frequent check-ups of the pool water by the managing authorities or state/central government bodies; improper and cheap equipment; overcrowding of pools; lack of seriousness and accountability; poor water quality; and the use of certain chemicals in higher quantities than is recommended by World Health Organization and CDC.

Among the observations yielded during discussions with the swimming training teams were comments to the effect that: there had been a lot of dental problems until 4 to 5 years ago, the problems are more frequent with certain pools and at some specified periods; the trainers have learned to recognize immediately after tasting the pool water whether or not it could lead to dental problems; almost every long-time swimmer develops some kind of dental problem; many times, swimmers have complained of sensitivity during swimming or immediately after swimming that is so severe, they are unable to eat or drink anything; and a sour taste in the mouth is very common.

To further establish a cause-effect relationship, prospective case-control studies on larger samples are needed. It would be impracticable to take pH values and acid content of pools each time the swimmer uses the pool. Swimmers’ erosion should be regarded as a result of cumulative exposures to varying pool chemistry over a period of time. Also, pool conditions can be replicated in the laboratory to certain limitations, and the effect on extracted teeth can be observed systematically.

Conclusion

Teeth are affected by various mechanical and chemical environmental insults on a regular basis. A continuous and repeated attack of a particular agent over a period of time may lead to various afflictions not only of the teeth but also of soft tissues. On the other hand, a short-term but strong exposure to deleterious environmental agents may also lead to various dental/oral afflictions. Teeth are exposed to these agents internally as well as externally. Exposures are also through various media and activities—eg, drinking, eating, swimming, biting, etc. One’s occupation is also of importance, and swimming is one of those occupations where cumulative insults by substandard water maintenance can have deleterious effects on the stability of dental tissues.

The prevalence of dental erosion and hypersensitivity among competitive swimmers is found to be significantly high. The exposure time and number of years spent practicing swimming is directly proportional to the prevalence of dental erosion and rough surfaces. Other problems frequently observed among swimmers are: sour mouth, tooth discoloration, and fracture of the incisal edges of teeth.

Acknowledgments

The authors would like to thank Mr. Ramchandra Nawar and Mr. Subroto Roy, Swimming Trainers at Thane Municipal Corporation’s Swimming Pool, Thane, India. Without their help, this study would have been impossible.

About the Authors

Om N. Baghele, MDS, MBA
Professor Department of Periodontology and Oral Implantology
SMBT Dental College and Hospital Sangamner
Maharashtra, India

Indranil A. Majumdar, MDS
Associate Professor
Department of Oral Pathology and Microbiology
Government Dental College and Hospital
Mumbai, India

Manojkumar S. Thorat, MDS
Senior Lecturer
Department of Periodontology and Dental Implantology
SMBT Dental College and Hospital
Sangamner, Maharashtra, India

Ramchandra Nawar, BSc
Trainer to swimmers
Thane Municipal Corporation
Thane, Mumbai, India

Mangala Om Baghele, BDS
Department of Pedodontics
Government Dental College and Hospital
Mumbai, India

Snehal Makkad, BDS
Private Practice
Mumbai, India